Disentangling the importance of determinism and stochasticity in structuring the phytoplanktonic metacommunity of the Paraná River Floodplain

DEVERCELLI, MELINA; MAYORA, GISELA; SCHNEIDER, BERENICE; SCARABOTI, PABLO

Kastoria

Workshop; 17th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP); 2014

International Association of Phytoplankton Taxonomy and Ecology (IAP)

In floodplain rivers, the main channel and the alluvial valley constitute a dynamic system integrated by the pulsing of water discharge. This configures a network of environments with different connectivity degree and capability to exchange organisms and matter. We use the metacommunity framework as a theoretical basis to study the phytoplankton assemblages in the Paraná River floodplain. We aim to examine the patterns of phytoplankton diversity across space and to identify the importance of stochastic and deterministic processes in structuring the assemblage. Two samplings (December 2013 and April 2014) were performed at 28 environments located in a hydrological connectivity gradient from the main channel to the more isolated floodplain water bodies. We considered for the analyses physical, chemical and hydrological variables, geographical coordinates, altitude, lake morphometry, connectivity degree, aquatic plant characterization, and phytoplankton composition and biovolume. We performed NPMANOVA and SIMPER to compare algal structure among habitats. As a measure of the importance of niche and stochastic processes, we considered the deviations from expectations by null models of the relationship between alfa (local species richness) and beta diversity of the studied sites (dissimilarity between sites). Additionally we decomposed the variation in beta diversity explained by spatial and local factors and the shared variation by a variance partition analysis.